flower, n. — Green’s Dictionary of Slang

flower n.

[the ‘feminine’ image of flowers]

1. an effeminate male homosexual.

1946		(con. 1914) B. Marshall George Brown’s Schooldays 167: ‘A filthy lot of ruins if you ask me, although one or two of them aren’t bad-looking,’ Hazel [i.e. a boy] said. ‘There’s a small chap with fair hair called Simpkins or Tompkins that I’m thinking of making my flower.’ Brown didn’t say anything. Ever since last summer hols with Rosalind he had come to the conclusion that he didn’t really like the idea of flowers, either being one or having one. It was ever so much more fun being in love with a girl.
1949		‘Hal Ellson’ Duke viii: Flower – a homosexual.
1964		Poston ‘Problems in the Study of Campus Sl.’ in AS XXXIX:2 118: Since the word pansy is available with reference to a male homosexual, the speaker is at liberty to substitute any number of flower names for the word and perhaps even refer to the person as simply a flower or plant.
1972		(ref. to early 1960s) B. Rodgers Queens’ Vernacular 44: Any boy under the age of consent [...] flower (kwn LV, early ’60s).

2. (N.Z. prison) an opium poppy.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 71/1: flower n. an opium poppy: ‘How're your flowers doing this season?’ Note: drug users ‘bleed the heads’ of opium poppies to obtain their milk, which is then used as a base for producing opiate-derived hard drugs such as heroin.

SE in slang uses

In compounds

flower-fancier (n.)

a womanizer, a lecher, presumably specializing in ‘flowers’, i.e. virgins.

1890–1904

Farmer & Henley Sl. and Its Analogues.

flower patch (n.)

(US) the female genital area.

1986

R. Campbell In La-La Land We Trust (1999) 149: If they get into long skirts, they got a slit up the front almost to the flower patch, and their tits is fallin’ out of the tops of their blouses.

flower-pot (n.)

the vagina.

1837–8		‘The Rare Old Root’ in Cuckold’s Nest 9: Then here’s too the root, the rare old root, / That stands whenever ’tis shown, / And still may it be to that flower pot free, / Which the ladies only own.
1896		Farmer Vocabula Amatoria (1966) 52: Calice, m. The female pudendum; ‘the flower-pot’.
2000		Desdemona at www.asstr.org 🌐 And then, finally, while she was touching her flowerpot with sticky fingers, that special joy Mama always talked about would shoot through her.

In phrases

flower in a wet spot (n.)

(N.Z.) a sexually aroused female.

2003

McGill Reed Dict. of N.Z. Sl.

flowers-on-his-grave (n.)

(Aus.) fastidiousness.

1919		W.H. Downing Digger Dialects 24: flowers-on-his-grave — Fastidiousness.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: flowers on his grave. Fastidious; hard to please, also port holes in his coffin.